Active region management techniques and associated methods of designing and manufacturing VLSI circuits

ABSTRACT

Disclosed herein is a method of determining an active region for a routing area having a plurality of component tiles positioned thereon. A set of stop points, each generally aligned with a lower edge of the routing area, an upper or lower edge of one of the component tiles, or an upper edge of the routing area, are determined. A component tile density interval is determined for a sweep line which corresponds to the lowermost stop point. The component tile density interval is then redetermined, in ascending order, for sweep lines generally aligned with each of the other stop points in the set. Along each sweep line, the component density is incremented by one for the horizontal span of a component tile for which the lower edge thereof extends therealong and decremented by one for the horizontal span of a component tile for which the upper edge thereof extends therealong.

CROSS REFERENCE TO RELATED APPLICATION

This application is related to U.S. patent application Ser. No. 10/109,125 entitled “A Maximal Tile Generation Technique and Associated Methods of Designing and Manufacturing VLSI Circuits”, filed on even date herewith, assigned to the Assignee of the present application and hereby incorporated by reference as if reproduced in its entirety.

BACKGROUND

1. Technical Field

This relates to the design and manufacture of very large scale integrated (“VLSI”) circuits and, more particularly, to an active region management technique suitable for use in conjunction with the design and manufacture of VLSI circuits.

2. Description of the Relevant Art

A VLSI circuit is typically composed of a plurality of layers, each having a plurality of generally rectangular shaped components positioned thereon, oriented in either the horizontal or vertical axis. VLSI circuit designers commonly refer to these generally rectangular shaped components as “component tiles” and to the generally rectangular shaped open spaces that surround the component tiles as “space tiles.” Component tiles that are to be connected on a VLSI circuit are said to form a “net”, while any component tile not connected to a particular net is considered to be an obstruction to that net. Two tiles are said to be “adjacent” if they touch along their edges and “overlapping” if there is even a single point located within the interior of both tiles. A set of tiles positioned within a routing area is said to be “maximal” if no two tiles are either overlapping or adjacent on their left or right edges.

One step in the design of a VLSI circuit is to select the wire paths that extend through the space tiles to connect the electrically equivalent component tiles that form nets. A current technique used to determine these paths utilizes a tile expansion algorithm. More specifically, clear space around the component tiles forming a net is fractured into maximal space tiles. Adjoining ones of these maximal space tiles are used to define the most efficient tile path between two components. The path of the actual connection between the components, known as the wire path, is then defined as the route through the space tile path from the component source tile to the component destination tile.

The aforementioned technique for selecting the wire paths for a VLSI circuit design suffers from two drawbacks, both of which may add to the cost of VLSI circuits manufactured in accordance with the design. First, if defined in accordance with the above-described manner, a tile path is not necessarily the optimal tile path through the clear space. Second, since the width of a tile path is typically much larger than the width of a wire path, multiple wire paths may exist through a given tile path. If the wire path located within the tile path is arbitrarily selected, the selected wire path is not necessarily the most efficient wire path potentially located within the tile path.

SUMMARY

Disclosed herein is a method and associated apparatus for determining an active region for a routing area having a plurality of components, each having a lower edge, an upper edge and a horizontal span, positioned thereon. A set of sweep lines, each extending along an upper or lower edge of at least one of the plurality of components, are determined for the routing area. A component tile density is determined along each one of the set of sweep lines. An active region for the routing area may then be generated from the component tile density along each one of the set of sweep lines. In determine component tile density along a sweep line, the component tile density is incremented by a pre-selected value for the horizontal span of a component tile upon encountering a lower edge thereof and decremented by the pre-selected value for the horizontal span of a component tile upon encountering an upper edge thereof.

The set of sweep lines may be arranged in an ascending order relative to an axis of the routing area and the component tile density determined, for the set of sweep lines, in the ascending order thereof. The first sweep line of the set of sweep lines is aligned with a lower edge of the routing area. For the first sweep line, the component tile density is set to zero at a first side edge of the routing area. A sweep is performed across the routing area and, for each lower edge or interior of a component tile encountered, the component tile density is incremented by the pre-selected value. For the next sweep line in the ascending order, the component tile density is initially set to that determined for the prior sweep line and subsequently adjusted for each lower or upper edge of a component tile encountered. Finally, for the uppermost sweep line in the ascending order, the component tile density is initially set to that determined for the prior sweep line and subsequently adjusted for each lower edge, interior or upper edge of a component tile encountered.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a computer system in which VLSI circuit design software resides.

FIG. 2 is a flow chart of a method for designing and manufacturing VLSI circuits.

FIG. 3a is a flow chart of a method, suitable for use in conjunction with the method of FIG. 2, for reconfiguring a non-maximal arrangement of component tiles positioned on a routing area into a maximal arrangement thereof.

FIG. 3b is a flow chart of a method, suitable for use in conjunction with the method for reconfiguring a non-maximal arrangement of component tiles of FIG. 3a, for determining an active region for a routing area.

FIG. 4 is a top view of a routing area having plural component tiles located thereon.

FIG. 5 is a top view of the routing area of FIG. 4 which shows an arrangement of maximal component and space tiles generated in accordance with the method of FIGS. 3a-b and fully populating the routing area.

DETAILED DESCRIPTION

Referring first to FIG. 1, a computer system 1, for example, a personal computer (“PC”), file server or other type of computer, in which VLSI circuit design software resides will now be described in greater detail. The computer system 1 is comprised of a processor subsystem 2, a memory subsystem 3 and an input/output (“I/O”) subsystem 4 coupled together by a bus subsystem 5. The bus subsystem 5 encompasses the main system bus and any local or other types of busses that collectively couple the processor subsystem 2, the memory subsystem 3 and the I/O subsystem 4 to one another. As used herein, the terms “couple” or “coupled” refer broadly to either direct or indirect connection.

The processor subsystem 2 encompasses the collective processing capability of the computer system 1, including the central processing unit (“CPU”) as well as any secondary processing devices, for example, an arithmetic processing unit, coupled to the CPU by the bus subsystem 5. Similarly, the memory subsystem 3 encompasses the collective storage capability of the computer system 1, including main, auxiliary, cache and any other memory accessible by the processor subsystem 2 via the bus subsystem 5. Finally, the I/O subsystem 4 encompasses any and all I/O devices, for example, floppy, CD-ROM or DVD drives, coupled to the bus subsystem 5, for writing data to or reading data from the processor subsystem 2 or the memory subsystem 3. The I/O subsystem 4 also encompasses any data communications equipment (“DCE”), for example, network interface cards or modems, which couple the computer system 1 to data terminal equipment (“DTE”), for example, a second PC, file server or web server, via a local area network (“LAN”), wide area network (“WAN”), intranet, internet or other type of network.

FIG. 1 further shows plural software modules, specifically, a first software module 6 for providing the computer system 1 with VLSI circuit design functionality, a second software module 7 for providing the computer system 1 with maximal tile generation functionality, a third software module 8 for providing the computer system 1 with active region management functionality and a fourth software module for providing the computer system 1 with connection routing functionality. Each of the software modules 6-9 is comprised of a series of instructions which are encoded in the memory subsystem 3 as computer readable program code and executable by the processor subsystem 2. Typically, the VLSI circuit design module 6, the maximal tile generation module 7, the active region management module 8 and the connection routing module 9 will be stored in the auxiliary memory of the memory subsystem 3 prior to the execution thereof. A transportable computer usable medium 10, for example, a floppy disk, CD-ROM or file transfer software, is used to copy the VLSI circuit design module 6, the maximal tile generation module 7, the active region management module 8 and the connection routing module 9 into the auxiliary memory of the memory subsystem 3.

As illustrated in FIG. 1, the functionality provided by the software modules 6-9 may be encoded in the memory subsystem 3 and/or the computer usable medium 10 as discrete computer programs, each containing computer readable program code. Alternately, the functionality provided by the software modules 6-9 may be encoded in the memory subsystem 3 and/or the computer usable medium 10 as separate subroutines of a single computer program containing plural computer readable program subcodes Furthermore, while any of the software modules 6-9 may be executed separately, typically, the VLSI circuit design module 6 will be initially executed by the processor subsystem 3. The VLSI circuit design module 6 will then periodically call selected ones of the maximal tile generation module 7, the active region management module 8 and the connection routing module 9 to perform certain functions during the design of a VLSI circuit. Of course, any one of the software modules 6-9 may call any other one of the software modules 6-9 to perform certain functions on its behalf.

Referring next to FIG. 2, a method for designing and manufacturing VLSI circuits will now be described in greater detail. The method commences at step 11 with the execution of the VLSI circuit design module 6 by the processor subsystem 2. The method proceeds to step 12 where a routing area is defined and a collection of component tiles are positioned thereon using the VLSI circuit design module 6. Generally, the routing area comprises the surface area of a level of an integrated circuit on which component tiles are positioned. For example, FIG. 4 illustrates component tiles (“CTs”) 92, 94, 96 and 98 positioned within a routing area 90. Wile, in the description to follow, the routing area 90 is oftentimes described with respect to a vertical axis, hereafter termed the “S” axis, which extends from S0 to S6, and a horizontal axis, hereafter termed the “D” axis, which extends from D0 to D7, it should be clearly understood that the use of these terms is not intended to imply or suggest that the routing area 90 has a particular orientation, either horizontal or vertical, relative to the VLSI circuit being designed. Likewise, the description of a first span (or segment thereof) of the routing area 90 as being located above or below a second span (or segment thereof) is not intended to imply or suggest that the first and second spans are oriented in either the horizontal or vertical plane. Rather, the use of these terms is merely intended to describe their relative location within a common plane without regard to the specific orientation of that plane.

Proceeding on to step 14, the CTs 92, 94, 96 and 98 are characterized as either maximal component tiles or non-maximal component tiles. In the example illustrated in FIG. 4, the CT 92 is a maximal component tile because there are no overlapping tiles or adjacent tiles on either the left or right sides. In contrast, the CTs 94, 96 and 98 are all non-maximal component tiles. Specifically, the CT 94 is a non-maximal component tile because a right side thereof overlaps a lower side of the CT 96. Similarly, the CT 98 is a non-maximal component tile because a left side thereof overlaps an upper side of the CT 96. Finally, the CT 96 is a non-maximal component tile because the lower side thereof is overlapped by the right side of the CT 94 and the upper side thereof is overlapped by the left side of the CT 98.

Proceeding on to step 15, if all of the CTs 92, 94, 96 and 98 are maximal component tiles, the method proceeds to step 20 for continued design and manufacture of the VLSI circuit. If, however, all of the CTs 92, 94, 96 and 98 are not maximal component tiles, the maximal tile generation module 7 is executed to reconfigure the non-maximal arrangement of the CTs 92, 94, 96 and 98 into a maximal component tile arrangement. Accordingly, the method proceeds to step 16 for construction of a maximal component tile list and a maximal space tile list. The method of constructing the maximal component tile list is described in greater detail below with respect to FIG. 3a. The method then proceeds on to step 18 where the maximal component tile and maximal space tile lists constructed at step 16 are used to position the maximal component tiles and maximal space tiles on the routing area 90.

Having repositioned the CTs 92, 94, 96 and 98 on the routing area 90 into a maximal arrangement at step 18 or after having determined that all of the CTs 92, 94, 96 and 98 were initially positioned in a maximal arrangement at step 15, the method proceeds to step 20 where the connection routing module 9 determines the optimal tile path, using space tiles, between pins that are CTs to be connected. Using the optimal tile path between pins that are CTs to be connected, the method continues on to step 24 where the positions of the CTs 92, 94, 96 and 98 and the wire path interconnecting the CTs are used by the VLSI circuit design module 6 to produce a VLSI circuit design. In this regard, it should be noted that the above-described technique provides the position for a single layer in either the horizontal or vertical planes of the VLSI circuit being designed. As VLSI circuits are typically multi-layer, the described process is repeated for each layer of the VLSI circuit in the selected plane. Furthermore, as a multi-layer VLSI typically includes connection paths along both the horizontal and vertical planes, the described process would also need to be repeated for each layer in the other one of the horizontal and vertical planes for which a connection path is needed. It should be noted, however, that the foregoing description of a method of designing a VLSI circuit is highly simplified and that numerous steps in the process which are deemed as not being needed for an understanding of the disclosed techniques have been omitted for ease of description. Having completed the design of the VLSI circuit, the method then continues on to step 26 where plural VLSI circuits which conform to the design are manufactured at a facility using conventional manufacturing processes. The method then ends at step 28.

Referring next to FIG. 3a, the method by which maximal component tile and maximal space tile lists are determined at step 16 will now be described in greater detail. The method commences at step 30 and, at step 32, a list (AL) of active segments and a list (IL) of inactive segments of a span which extends along a bottom edge of the routing area 90 are identified. Generally, an “active” segment of a span is a segment which passes through the interior of a component tile or along a lower edge thereof. Conversely, an “inactive” segment of a span is a segment that passes through an unoccupied portion of the routing area or along an upper edge of a component tile. Once active and inactive segments of the span have been identified, a level is then assigned to each segment thereof. The level of a segment is the point, along the S axis, generally aligned with the span of which the active or inactive segment forms a portion thereof. For example, a segment forming part of a span may be described as follows: [DX, DY, SZ] where DX is the point, along the D axis, where the active or inactive segment starts, DY is the point, along the D axis, where the active or inactive segment ends and SZ is the level, along the S axis, of the active or inactive span of which the active or inactive segment forms a portion thereof.

An active segment of a first span may be said to “match” an active segment of a second span if the segments have the same start point DX and the same stop point DY along the D axis but different levels SZ along the S axis. For example, the active segments [D1, D3, S1] and [D1, D3, S2] are considered to be matching active segments. Conversely, the term “unmatched” active segments refer to spans which, in addition to having different levels SZ, also have different start points DX, different stop points DY or both. Likewise, an inactive segment of a first span matches an inactive segment of a second span if the segments have the same start and stop points DX and DY but different levels SZ while unmatched inactive segments also have either a different start point DX, a different stop point DY or both.

A “characteristic” of a span is defined by the set of segments which comprises the span. A pair of spans may be deemed as having the same characteristic if every active and inactive segment of a first span of the span pair has a matching active or inactive segment, respectively, in a second one of the span pair. Conversely, a pair of spans may be deemed as having different characteristics if every active and inactive segment of the first span fails to have a matching active or inactive segment, respectively, in the second span.

As may be clearly seen in FIG. 4, neither a lower edge nor an interior of a component tile extends along the bottom edge of the routing area 90. Accordingly, the bottom edge of the routing area 90 has a span comprised of a single inactive segment which extends from D0 to D7. As may be further seen in FIG. 4, the level of the span is S0. The level of the span is hereby designated as a first stop point S0 for a set of stop points for the routing area 90 and the list of active and inactive segments of the span which extends along the bottom edge of the routing area 90 and is generally aligned with the first stop point S0 may be described as follows:

AL={ };and

IL={[D 0, D 7, S 0]}.

The list of ALs and the list of ILs for the span generally aligned with the first stop point S0 are hereby designated as a current list of ALs and a current list of ILs, respectively, for the routing area 90.

Continuing on to step 34, additional members of the set of stop points for the routing area 90 are identified. These additional stop points for the routing area 90 are those points along the S axis which are generally aligned with either a lower edge of one or more of the CTs 92, 94, 96 and 98 and/or an upper edge of one or more of the CTs 92, 94, 96 and 98. Thus, from the known arrangement of the CTs 92, 94, 96 and 98 illustrated in FIG. 4, the maximal tile generation module 7 identifies, in an ascending order relative to the S axis, S1, S2, S3, S4 and S5 as additional members of the set of stop points for the routing area 90. Finally, an upper edge of the routing area 90 is designated as a last stop point S6 of the set of stop points for the routing area 90. The method then proceeds to step 36 where an empty list of maximal component tiles (CTL) and an empty list of maximal space tiles (STL) are generated.

S1, S2, S3, S4, S5 and S6 were identified as additional stop points because they are all aligned with one or more of the lower edges of the CTs 92, 94, 96 and 98, the upper edges of the CTs 92, 94, 96 and 98 and/or the upper edge of the routing area 90. The edges of the CTs 92, 94, 96 and 98 are used to identify additional stop points since the edges of a CT indicate transition between active and inactive regions. More specifically, a lower edge of a CT indicates the location of an inactive-to-active transition while an upper edge of a CT indicates the location of an active-to-inactive transition. The stop points are selected to coincide with either inactive-to-active or active-to-inactive transitions because, in accordance with the techniques disclosed herein and to be more fully described below, maximal component and/or space tiles are generated whenever active and/or inactive segments of a first span fails to have a matching active and/or inactive segments along a second span.

At step 38, it is determined whether there are additional stop points which require examination. If so, the method proceeds to step 40 for selection of a next stop point for examination. At step 42, a next list of active segments and a next list of inactive segments are identified for a next span generally aligned with a next stop point of the set of stop points. The lists of active and inactive segments of the span generally aligned with the next stop point are generated using the active region management techniques disclosed herein with respect to FIG. 3b.

The active region for the routing area 90 may be readily determined using the collective list of active and inactive segments for each span generally aligned with one of the stop points of the set of stop points. More specifically, from the list of active and inactive segments for a stop line, a sequence of density intervals may be determined for that stop line. Each density interval has the same number (density) of covering CTs. The consecutive non-zero-density density intervals form an active region. The span of the active region for the routing area 90 is the union of these non-zero density intervals. Inactive regions for the routing area 90 are those zero-density density intervals. In accordance therewith, and referring momentarily to FIG. 3b, a technique by which a list of active and inactive segments for a span generally aligned with a selected stop point is generated at step 42 will now be described in detail. By obtaining such a list of active and inactive segments for each span corresponding to one of the set of stop points, the active region for the routing area 90 may be obtained.

The method commences at step 42-1 and, at step 42-2, a sweep across the span generally aligned with the selected stop point is initiated. Initially, the component tile density interval γ along the span is identically set to the component tile density interval for a prior sweep across the routing area 90. The component tile density interval γ along the span is then modified appropriated based upon the component tiles encountered during the sweep. In this regard, it should be noted that a sweep along a span generally aligned with a selected stop point may or may not result in the component tile density along the span line being adjusted. More specifically, during each sweep across the routing area 90, one or more upper and/or lower edge of component tiles may be encountered. If a lower edge of a component tile is encountered during the sweep, the component tile density along the span is incremented by one for that portion of the span occupied by the lower edge of the encountered component tile. Conversely, if an upper edge of a component tile is encountered during the sweep, the component tile density along the span is decremented by one, again for that portion of the span occupied by the upper edge of the component tile.

Thus, proceeding on to step 42-3, if a lower or upper edge of a component tile is encountered during the sweep across the span generally aligned with the selected stop point, the method proceeds to step 42-4 where the component tile density interval γ is modified for a segment of the span corresponding to the lower or upper edge of the encountered tile. After modifying the CT density for the segment of the span corresponding to the lower or upper edge of the encountered tile at step 42-4 or if, at step 42-3, a component tile was not encountered during the sweep, the method proceeds to step 42-5 for a determination as to whether the sweep has reached the end of the span. If the sweep has not yet reached the end of the span, the sweep continues at step 42-6 and the method returns to step 42-3 for further processing during which the component tile density interval γ will be further modified for each additional upper or lower edge of a component tile encountered during the sweep across the routing area 90. If, however, the sweep is completed and no further upper or lower edges of component tiles are encountered, the method will then proceed to step 42-7 for generation of the active and inactive segment lists AL and IL from the component tile density interval γ. The method then ends at step 42-8.

In accordance with the methods described herein, active and inactive segment lists AL and IL shall now be generated for stop points S1 through S6. As will be more fully described below, these active and inactive segment lists are later used to generate maximal component and space tile lists CTL and STL. Initially, the tile density interval for the span generally aligned with the stop point S0 is determined using the list of active and inactive segments for the bottom edge 90 a of the routing area 90. For this edge, it was previously determined that:

AL={ }; and

IL={[D 1, D 7, S 0]}.

Thus, as there are neither an interior nor a lower edge of a component tile extending along the bottom edge 90 a of the routing area 90, the initial component tile density interval γ for the span is:

γ=[D 0, D 7, 0].

Of course, in the event that the component tiles were positioned in the routing area 90 such that overlapping component tiles extended along the bottom edge 90 a of the routing area, density intervals along the bottom edge 90 a may be determined by breaking the bottom edge 90 a into small pieces such each sub-interval thereof has the same number of covering CTs.

A sweep along the span generally aligned with the stop point S1 encounters the lower edge 92 a of the CT 92 from D1 to D2, the lower edge 94 a of the CT 94 from D3 to D5 and the lower edge 96 a of the CT 96 from D4 to D5. Thus, the component tile density interval γ, which is incremented by 1 from D1 to D2 and from D3 to D4 because the lower edges 92 a and 94 a of the CTs 92 and 94 were encountered during these sub-intervals and is incremented by 2 from D4 to D5 because both the lower edge 94 a of the CT 94 and the lower edge 96 a of the CT 96 were encountered during this sub-interval, may be expressed as follows:

γ={[D 0, D 1, 0], [D 1, D 2, 1], [D 2, D 3, 0], [D 3, D 4, 1], [D 4, D 5, 2], [D 5, D 7, 0]}.

From the aforementioned component tile density intervals, the following next active and inactive segment lists may be derived for the sweep line generally aligned with the stop point S1:

 AL={[D 1, D 2, S 1], [D 3, D 5, S 1]}; and

IL={[D 0, D 1, S 1], [D 2, D 3, S 1], [D 5, D 7, S 1]}.

A sweep along the span generally aligned with the stop point S2 encounters the upper edge 94 b of the CT 94 from D3 to D5. Thus, the component tile density interval, which is decremented by 1 from D3 to D5, may be expressed as follows:

γ={[D 0, D 1, 0], [D 1, D 2, 1], [D 2, D 4, 0], [D 4, D 5, 1], [D 5, D 7, 0]}.

From the aforementioned component tile density intervals, the following next active and inactive segment lists may be derived for the sweep line generally aligned with the stop point S2:

AL={[D 1, D 2, S 2], [D 4, D 5, S 2]}; and

IL={[D 0, D 1, S 2], [D 2, D 4, S 2], [D 5, D 7, S 2]}.

A sweep along the span generally aligned with the stop point S3 encounters the upper edge 92 b of the CT 92 from D1 to D2. Thus, the component tile density interval, which is decremented by 1 from D1 to D2 may be expressed as follows:

γ={[D 0, D 4, 0], [D 4, D 5, 1], [D 5, D 7, 0]}.

From the aforementioned component tile density intervals, the following next active and inactive segment lists may be derived for the sweep line generally aligned with the stop point S3:

AL={[D 4, D 5, S 3]}; and

IL={[D 0, D 4, S 3], [D 5, D 7, S 3]}.

A sweep along the span generally aligned with the stop point S4 encounters the lower edge 98 a of the CT 98 from D4 to D6. Thus, the component tile density, which is incremented by 1 from D4 to D6, may be expressed as follows:

γ={[D 0, D 4, 0], [D 4, D 5, 2], [D 5, D 6, 1], [D 6, D 7, 0]}.

From the aforementioned component tile density intervals, the following next active and inactive segment lists may be derived for the sweep line generally aligned with the stop point S4:

AL={[D 4, D 6, S 4]}; and

IL={[D 0, D 4, S 4], [D 6, D 7, S 4]}.

A sweep along the span generally aligned with the stop point S5 encounters the upper edge 96 b of the CT 96 from D4 to D5 and the upper edge 98 b of the CT 98 from D4 to D6. Thus, the component tile density, which is decremented by 2 from D4 to D5 and decremented by 1 from D5 to D6, may be expressed as follows:

γ={[D 0, D 7, 0]}

From the aforementioned component tile density intervals, the following next active and inactive segment lists may be derived for the sweep line generally aligned with the stop point S5:

AL=Φ; and

IL={[D 0, D 7, S 5]}.

A sweep along the span generally aligned with the stop point S6 does not encounter the lower edge of any component tiles. Thus, the component tile density, which remains unchanged, may be expressed as follows:

γ={[D 0, D 7, 0]}.

From the aforementioned component tile density intervals, the following next active and inactive segment lists may be derived for the sweep line generally aligned with the stop point S6:

AL=Φ; and

IL={[D 0, D 7, S 6]}.

Having generated a list of active and inactive segments for the span generally aligned with each one of the stop points S0, S1, S2, S3, S4, S5 and S6, the active region for the routing area 90 may now be generated. As previously set forth, the active region is collectively described by the list of active and inactive segments for the spans corresponding to each one of the stop points S0 through S6 for the routing area.

Returning now to FIG. 3a, having generated the next list of active segments and the next list of inactive segments of the span generally aligned with the next stop point at step 42, the method proceeds to step 44 where the next list of active segments is compared to the current list of active segments and, based upon that comparison, one or more maximal component tiles may be identified for inclusion in the list of maximal component tiles.

More specifically, for each active segment S in the current list of active segments, the next list of active segments is examined for a matching active segment S′. If there is no matching active segment S′ in the next list of active segments, a maximal component tile having a width generally equal to the width [DX, DY] of the active segment S and a height generally equal to the difference between the level of the active segment S and the level of the active segment S′ is generated. The generated maximal component tile is then inserted into the maximal component tile list CTL and the active segment S removed from the current list of active segments. After searching for a matching active segment S′ in the next active segment list for each active segment S in the current active segment list, any unmatched active segment S′ in the next active segment list is added to the current active segment list. Initially, the current active segment list will contain active segments at only one level. It should be noted, however, as the next active segment lists for various levels are examined, the current active segment list will likely contain active segments at plural levels.

The method then proceeds to step 46 where the process of step 45 is repeated using the current and next list of inactive segments. By doing so, one or more maximal space tiles may be generated at step 44 and added to the maximal space tile list STL. Additionally, the current list of inactive segments will be modified by deleting the inactive segments, from the current list of inactive segments, the inactive segments having a matching inactive segment in the next list of inactive segments and by adding, to the current list of inactive segments, unmatched inactive segments from the next list of inactive segments. The method then returns to step 38 where the process described in steps 40, 42, 44 and 46 is repeated for each stop point in the set of stop points. After the last stop point in the set of stop points has been processed, the method will proceed from step 38 to step 48 where the maximal component tile list CTL and the maximal space tile list STL generated by the described method are output, typically, to the VLSI circuit design module 8 for use in connection with the design and manufacture of a VLSI circuit in accordance with the method of FIG. 2.

The above-described method of generating a list of maximal component tiles CTL and a list of maximal space tiles STL for the routing area 90 shall again be described, now with respect to the example illustrated in FIGS. 4 and 5. As previously noted, FIG. 4 shows the CTs 92, 94, 96 and 98 positioned in the routing area 90 in a non-maximal tile arrangement. However, by applying the process set forth in FIG. 3 to the non-maximal component tile arrangement of FIG. 4, the component tiles are re-configured into the maximal tile arrangement illustrated in FIG. 5. As previously set forth, the process starts at step 32 by identifying the active and inactive segments for a span extending along a bottom edge 90 a of the routing area 90. As there are no active segments along the bottom edge 90 a, the current active and inactive segment lists for this span, which is generally aligned with the stop point S0, are initially set as follows:

AL={ }; and

IL={[D 0, D 7, S 0]}.

At step 34, the remaining members of the set of stop points are identified (S1, S2, S3, S4, S5 and S6) and, at step 36, an empty maximal component tile list CTL and an empty maximal space tile list STL are generated. As the stop points S1 through S6 need to be examined, the method passes through 38 and on to step 40 where the stop point S1, the next stop point after the stop point S0, is selected for examination. As may be seen in FIG. 4, bottom edges 92 a, 94 a and 96 a of the CTs 92, 94 and 96, respectively, are generally aligned with the stop point S1. The corresponding segments are, therefore, considered to be active while the remaining segments generally aligned with the stop point S1 are considered to be inactive. Accordingly, at step 42, the next list of active segments and the next list of inactive segments are determined to be:

AL={[D 1, D 2, S 1], [D 3, D 5, S 1]}; and

IL={[D 0, D 1, S 1], [D 2, D 3, S 1], [D 5, D 7, S 1]}.

Proceeding to step 44, the current active segment list is empty. As a result, there are no matches between the current list of active segments and the next list of active segments. As a result, no maximal component tiles are generated at step 44. Furthermore, as both entries in the next active segment list are unmatched, they are added to the current active segment list, which now becomes:

AL={[D 1, D 2, S 1]. [D 3, D 5, S 1]}.

The method then proceeds to step 46 for processing of the current inactive segment list. The current inactive segment list contains a single entry [D0, D7, S0]. As there is no matching span in the next inactive segment list, a space tile, hereafter referred to as ST 100 and illustrated in FIG. 5, which extends from D0 to D7 in the D axis along a line generally aligned with S0 and which extends from S0 to S1 in the S axis is generated and added to the maximal space tile list STL. The unmatched entry [D0, D7, S0] is deleted from the current inactive segment list and the unmatched entries [D0, D1, S1], [D2, D3, S1] and [D5, D7, S1] of the next inactive segment list are added to the current inactive segment list, thereby producing the following current inactive segment list:

IL={[D 0, D 1, S 1], [D 2, D 3, S 1], [D 5, D 7, S 1]}.

The method then returns to step 38 and, as there are additional stop points to be examined, on to step 40 where stop point S2 is selected for examination.

A span extending across the routing area 90 along a line generally aligned with the stop point S2 passes through the interior of the CT 92, along an upper edge 94 b of the CT 94 and through the interior of the CT 96. Accordingly, the next list of active and inactive segments would be as follows:

AL={[D 1, D 2, S 2], [D 4, D 5, S 2]}; and

IL={[D 0, D 1, S 2], [D 2, D 4, S 2], [D 5, D 7, S 2]}

For each active segment in the current active segment list, the next active segment list is searched for matches. Here, the [D1, D2, S1] entry from the current active segment list matches the [D1, D2, S2] entry from the next active segment list while the [D3, D5, S1] entry from the current active segment list is unmatched. Accordingly, a maximal component tile, hereafter referred to as CT 102 and illustrated in FIG. 5, which extends from D3 to D5 in the D axis along a line generally aligned with S1 and which extends from S1 to S2 in the S axis is generated and added to the maximal component tile list CTL. The matched entry [D3, D5, S1] is then deleted from the current active segment list while the unmatched entry [D4, D5, S2] from the next active segment list is added to the current active segment list, thereby producing the following current active segment list:

 AL={[D 1, D 2, S 1], [D 4, D 5, S 2]}.

The method then proceeds to step 46 for processing of the current inactive segment list. The current inactive segment list contains entries [D0, D1, S1], [D2, D3, S1] and [D5, D7, S1] while the next inactive segment list contains entries [D0, D1, S2], [D2, D4, S2] and [D5, D7, S2]. Thus, the [D0, D1, S1] and [D5, D7, S1] entries of the current inactive segment list are matched while the [D2, D3, S2] entry is unmatched. Accordingly, maximal space tile ST 104, which extends from D2 to D3 in the D axis along a line generally aligned with S1, extends from S1 to S2 in the S axis and is illustrated in FIG. 5, is generated and added to the maximal space tile list STL. The matched entry is then deleted from the current inactive segment list while the unmatched entry [D2, D4, S2] of the next inactive segment list is added to the current inactive segment list, thereby producing the following current inactive segment list:

IL {[D0, D 1, S 1], [D 2, D 4, S 2], [D 5, D 7, S 1]}.

A span extending across the routing area 90 along a line generally aligned with the stop point S3 passes along an upper edge 92 b of the CT 92 and through the interior of the CT 96. Accordingly, the next list of active and inactive spans would be as follows:

AL={[D 4, D 5, S 3]}; and

IL={[D 0, D 4, S 3], [D 5, D 7, S 3]}.

For each active span in the current active segment list, the next active segment list is searched for matches. Here, the entry [D4, D5, S1] matches the entry [D4, D5, S3] while the entry [D1, D2, S1] is unmatched. Accordingly, the entry [D1, D2, S1] is used to generate a maximal component tile, hereafter referred to as CT 106 and illustrated in FIG. 5, which extends from D1 to D2 in the D axis along a line generally aligned with S1 and from S1 to S3 in the S axis. The newly generated maximal component tile is then added to the maximal component tile list CTL. The matched entry [D1, D2, S1] is deleted from the current active segment list and, since there are no unmatched entries from the next active segment list, the following current active segment list is produced:

AL={[D 4, D 5, S 2]}.

The method then proceeds to step 46 for processing of the current inactive segment list. The current inactive segment list contains entries [D0, D1, S1], [D2, D4, S2] and [D5, D7, S1] while the next inactive segment list contains entries [D0, D4, S3] and [D5, D7, S3]. Thus, the [D5, D7, S1] entry of the current inactive segment list is matched while the [D0, D1, S1] and [D2, D4, S2] entries of the current inactive segment list are unmatched. Accordingly, the unmatched entry [D0, D1, S1] is used to generate maximal space tile ST 108, which extends from D0 to D1 in the D axis along a line generally aligned with S1, extends from S1 to S3 in the S axis and is illustrated in FIG. 5. Furthermore, the unmatched entry [D2, D4, S2] is used to generate maximal space tile ST 110, which extends from D2 to D4 in the D axis along a line generally aligned with S2, extends from S2 to S3 in the S axis and is illustrated in FIG. 5. The newly generated tiles are then added to the maximal space tile list, the unmatched entries [D0, D1, S1] and [D2, D4, S2] are deleted from the current inactive segment list and the unmatched entry [D0, D4, S3] of the next inactive segment list is added to the current inactive segment list, thereby producing the following current inactive segment list:

IL={[D 0, D 4, S 3], [D 5, D 7, S 1]}.

The method then returns to step 38 and, as there are additional stop points to be examined, on to step 40 where stop point S4 is selected for examination.

A span extending across the routing area 90 along a line generally aligned with the stop point S4 extends through the interior of the CT 96 and along a lower edge 98 a of the CT 98. Accordingly, the next list of active and inactive spans generated at step 42 would be as follows:

AL={[D 4, D 6, S 4]}; and

IL={[D 0, D 4, S 4], [D 6, D 7, S 4]}.

The current and next active segment lists are then processed at step 44. The current active segment list is [D4, D5, S2] while the next active segment list is [D4, D6, S4]. Thus, there are no matches between the current and next active segment lists. Accordingly, the entry [D4, D5, S2] of the current active segment list is used to generate a maximal component tile, hereafter referred to as CT 112 and illustrated in FIG. 5, which extends from D4 to D5 in the D axis along a line generally aligned with S2 and from S2 to S4 in the S axis. The newly generated maximal component tile is then added to the maximal component tile list CTL. The unmatched entry [D4, D5, S2] is then deleted from the current active segment list and the unmatched entry [D4, D6, S4] from next active segment list is added to the current active segment list to produce the following current active segment list:

AL={[D 4, D 6, S 4]}.

The method then proceeds to step 46 for processing of the current inactive segment list. The current inactive segment list contains entries [D0, D4, S3] and [D5, D7, S1] while the next inactive segment list contains entries [D0, D4, S4] and [D6, D7, S4]. Thus, the [D0, D4, S3] entry of the current inactive segment list is matched to the entry [D0, D4, S4] entry of the next inactive segment list while the [D5, D7, S1] entry of the current inactive segment list and the [D6, D7, S4] entry of the next inactive segment list are unmatched. Accordingly, the unmatched entry [D5, D7, S1] of the current active span is used to generate maximal space tile ST 114, which extends from D5 to D7 in the D axis along a line generally aligned with S1, extends from S1 to S4 in the S axis and is illustrated in FIG. 5. The newly generated space tile is then added to the maximal space tile list STL, the unmatched entry [D5, D7, S1] is deleted from the current inactive segment list and the unmatched entry [D6, D7, S4] of the next inactive segment list is added to the current inactive segment list, thereby producing the following current inactive segment list:

IL={[D 0, D 4, S 3], [D 6, D 7 S 4]}.

The method then returns to step 38 and, as there are additional stop points to be examined, on to step 40 where stop point S5 is selected for examination.

A span extending across the routing area 90 along a line generally aligned with the stop point S5 passes along the upper edge of the CT 96 and the upper edge of the CT 98. Accordingly, the next list of active and inactive spans generated at step 42 would be as follows:

AL={ };and

IL={[D 0, D 7, S 5]}.

The current and next active segment lists are then processed at step 44. The current active segment list is [D4, D6, S4] while the next active segment list is empty. Thus, there are no matches between the current and next active segment lists. Accordingly, the entry [D4, D5, S4] of the current active segment list is used to generate a maximal component tile, hereafter referred to as CT 116 and illustrated in FIG. 5, which extends from D4 to D6 in the D axis along a line generally aligned with the stop point S4 and from the stop point S4 to the stop point S5 in the S axis. The newly generated maximal component tile is then added to the maximal component tile list CTL. The unmatched entry [D4, D6, S4] is then deleted from the current active segment list and, since the next active segment list is empty, the current active segment list becomes empty as well.

The method then proceeds to step 46 for processing of the current inactive segment list. The current inactive segment list contains entries [D0, D4, S3] and [D6, D7, S4] while the next inactive segment list contains the entry [D0, D7, S5]. Thus, the [D0, D4, S3] and [D6, D7, S4] entries of the current inactive segment list and the [D0, D7, S5] entry of the next inactive segment list are unmatched. Accordingly, the unmatched entry [D0, D4, S3] of the current inactive span is used to generate maximal space tile ST 118, which extends from D0 to D4 in the D axis along a line generally aligned with S3 and which extends from S3 to S5 in the S axis while the unmatched entry [D6, D7, S4] of the current inactive span is used to generate maximal space tile ST 120 which extends from D6 to D7 in the D axis along a line generally aligned with S4 and which extends from S4 to S5 in the S axis. The newly generated space tiles ST 118 and ST120, both of which are illustrated in FIG. 5, are then added to the maximal space tile list STL, the unmatched entries [D0, D4, S3] and [D6, D7, S4] are deleted from the current inactive segment list and the unmatched entry [D0, D7, S5] of the next inactive segment list is added to the current inactive segment list, thereby producing the following current inactive segment list:

IL={[D 0, D 7, S 5]}.

The method then returns to step 38 and, as there are additional stop points to be examined, on to step 40 where the stop point S6 is selected for examination.

A span extending across the routing area 90 along a line generally aligned with the stop point S6 passes along the upper edge 90 b of the routing area 90. As neither a lower edge nor an interior of a component is positioned along the upper edge 90 b, the next list of active and inactive spans generated at step 42 would be as follows:

 AL={ }; and

IL={[D 0, D 7, S 6]}.

The current and next active segment lists are then processed at step 44. The current active segment list is empty while the next active segment list is empty. As both the current and next active segment lists are empty, no additional maximal component tiles are generated and the current active segment list remains empty.

The method then proceeds to step 46 for processing of the current inactive segment list. The current inactive segment list contains entries [D0, D7, S5] while the next inactive segment list contains the entry [D0, D7, S6]. While the current and inactive segment lists contain matching entries, the stop point being examined is the last stop point in the set of stop points. Accordingly, the [D0, D7, S5] entry of the current inactive segment list is used to generate a maximal space tile, hereafter referred to as maximal space tile 122, which extends from D0 to D7 in the D axis along a line generally aligned with S5, extends from S5 to S6 in the S axis and is illustrated in FIG. 5. The newly generated space tile is added to the maximal space tile list STL and the entry [D0, D7, S5] of the current inactive segment list is deleted therefrom, thereby emptying it. Further, as the entry [D0, D7, S6] was matched to the entry [D0, D7, S5], it is not added to the current inactive segment list, thereby keeping the current inactive segment list empty.

The method then returns to step 38 where, as all of the stop points S0 through S6 have been examined, to step 48 for output of the generated maximal component tile and maximal space tile lists CTL and STL. The method then ends at step 50.

Thus, there has been described and illustrated herein, active region management techniques suitable for use in conjunction with the design and manufacture of VLSI circuits. However, those skilled in the art should recognize that numerous modifications and variations may be made in the techniques disclosed herein without departing substantially from the spirit and scope thereof, which is defined solely by the claims appended hereto. 

What is claimed is:
 1. For a routing area having a plurality of components positioned thereon, a method for determining an active region for said routing area, comprising: determining a set of sweep lines for a routing area having a plurality of component tiles positioned thereon, each one of said set of sweep lines extending along an upper or lower edge of at least one of said plurality of components; determining component tile density interval along each one of said set of sweep lines; and generating a list of active and inactive segments from said component tile density interval along each one of said sweep lines to determine said active region for said routing area.
 2. The method of claim 1, wherein each one of said plurality of component tiles has a lower edge, an upper edge and a horizontal span and wherein determining component tile density interval along each one of said set of sweep lines further comprises: upon encountering a lower edge of a component tile along a sweep line, incrementing component tile density interval by a pre-selected value along said horizontal span thereof; and upon encountering an upper edge of a component tile along a sweep line, decrementing component tile density interval by said pre-selected value along said horizontal span thereof.
 3. The method of claim 1, wherein determining a set of sweep lines for a routing area further comprises arranging said sweep lines in an ascending order relative to an axis of said routing area.
 4. The method of claim 3, wherein: said routing area has a lower edge, an upper edge, a first side edge and a second side edge; each one of said plurality of component tiles has a lower edge, an upper edge and a horizontal span; and determining component tile density interval along each one of said set of sweep lines further comprises: selecting, from said set of sweep lines, a first sweep line for which said component tile density interval is to be determined, said selected sweep line being generally aligned with said lower edge of said routing area; setting said component tile density interval along said selected sweep line to zero at said first side edge of said routing area; performing a sweep across said routing area along said selected sweep line; for each lower edge of a component tile encountered during said sweep across said routing area along said selected sweep line, incrementing component tile density interval by said pre-selected value along said horizontal span of said encountered tile; and for each upper edge of a component tile encountered during said sweep across said routing area along said sweep line, decrementing component tile density interval by said pre-selected value along said horizontal span of said encountered tile.
 5. The method of claim 4, wherein determining component tile density interval along each one of said set of sweep lines further comprises: selecting, from said set of sweep lines, a next sweep line for which said component tile density interval is to be determined, said next selected sweep line being next in said ascending order along said longitudinal axis of said area; setting said component tile density interval along said next selected sweep line to match said component tile density for said selected sweep line; performing a sweep across said routing area along said next selected sweep line; for each lower edge of a component tile encountered during said sweep across said routing area along said next selected sweep line, incrementing component tile density interval by a pre-selected value along said horizontal span of said encountered tile; and for each upper edge of a component tile encountered during said sweep across said routing area along said next selected sweep line, decrementing component tile density interval by said pre-selected value along said horizontal span of said encountered tile.
 6. The method of claim 5, and further comprising repeating each part of claim 5 for each remaining one of said set of sweep lines not generally aligned with an upper edge of said routing area.
 7. The method of claim 6, and further comprising: selecting, from said set of sweep lines, a last sweep line for which said component tile density interval is to be determined, said last selected sweep line being generally aligned with said upper edge of said routing area; setting said component tile density interval along said last selected sweep line to match said component tile density interval for an uppermost one of said sweep lines below said upper edge of said routing area; performing a sweep across said routing area along said last selected sweep line; for each lower edge of a component tile encountered during said sweep across said routing area along said last selected sweep line, incrementing component tile density interval by a preselected value along said horizontal span of said encountered tile; and for each upper edge of a component tile encountered during said sweep across said routing area along said last selected sweep line, decrementing component tile density interval by said pre-selected value along said horizontal span of said encountered tile.
 8. A computer system, comprising: a memory subsystem; a processor subsystem; a bus subsystem, said bus subsystem coupling said memory subsystem and said processor subsystem for the exchange of signals therebetween; and a VLSI circuit design module, said VLSI circuit design module stored in said memory subsystem and executable by said processor subsystem; said VLSI circuit design module comprising: means for configuring a routing area for a layer of a VLSI circuit design, said routing area having a plurality of component tiles positioned thereon; means for generating a plurality of sweep lines which extend longitudinally across an active region of said routing area; means for determining component tile density interval along each one of said plurality of generated sweep lines; means for generating a list of active and inactive segments from said component tile density interval along each one of said sweep lines to determine said active region for said routing area; and means for reconfiguring said plurality of component tiles positioned in said routing area into a maximal arrangement; wherein, in determining said maximal arrangement of said plurality of component tiles, said reconfiguring means using said active region determined by said active region determination means.
 9. For a routing area having a plurality of components positioned thereon, a method for determining an active region for said routing area, comprising: determining a set of stop points for said routing area having a plurality of component tiles positioned thereon; determining component tile density interval along a sweep line generally aligned with a first one of said set stop points; redetermining said component tile density interval along a sweep line generally aligned with a next one of said set of stop points using said component tile density interval for said first one of said set of stop points; and generating a list of active and inactive segments from said component tile density interval along each one of said sweep lines to determine said active region for said routing area.
 10. A computer program product, comprising: a computer usable medium; and computer readable program code, encoded in said computer usable medium, and executable to: determining a set of sweep lines for a routing area having a plurality of component tiles positioned thereon, each one of said set of sweep lines extending along an upper or lower edge of at least one of said plurality of components; determining component tile density interval along each one of said set of sweep lines; and generating a list of active and inactive segments from said component tile density interval along each one of said sweep lines to determine said active region for said routing area.
 11. The computer program product of claim 10, wherein: each one of said set of sweep lines is aligned with a lower edge of said routing area, the upper or lower edge of at least one of said plurality of components or an upper edge of said routing area; and said computer readable program code is further executable to redetermine said component tile density along said sweep lines in an ascending order along an axis of said routing area.
 12. A computer system, comprising: a memory subsystem; a processor subsystem; a bus subsystem, said bus subsystem coupling said memory subsystem and said processor subsystem for the exchange of signals therebetween; and an active region management module, said active region management module stored in said memory subsystem and executable by said processor subsystem to: determine a set of sweep lines for a routing area having a plurality of component tiles positioned thereon, each one of said set of sweep lines extending along an upper or lower edge of at least one of said plurality of components; determining component tile density interval along each one of said set of sweep lines; and generating a list of active and inactive segments from said component tile density interval along each one of said sweep lines to determine said active region for said routing area.
 13. The computer system of claim 12, wherein said active region management module is further executable by said processor subsystem to determine said component tile density interval for a next one of said set of sweep lines using said component tile density interval previously determined for a prior one of said set of sweep lines. 